Lesson 7: Create the code for the ValueParamValidator class

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The ValueParamValidator class handles the verification of the Value parameter in the HowTo action. This lesson describes in detail how to create the code to demonstrate the parameter verification and validation features of the com.ibm.carma.ui.parameterValidators extension point.

About this task

For this sample, the following are a list of possible inputs from the user and the informational messages that are displayed.
  • When the user enters a 0, an informational message is displayed
  • When the user enters a 1, a warning message is displayed
  • When the user enters a value of 2 or greater, an error message is displayed
  • When the user enters a non-numeric character, the input will not be allowed

Procedure

  1. In the Package Explorer view, open the ValueParamValidator class by navigating com.ibm.carma.plugin.howto > src > com.ibm.carma.plugin.howto.action and double-clicking on the class to open it in the editor.
  2. You will first implement the verifyInput method. This method checks for any invalid characters in the input text. For this sample, this method will only accept numeric characters. The following pseudocode demonstrates this: 
    if the length of input is greater than 0
   then allow input if the input characters are 0-9
else
   do not allow input
    Use the following example sample code to implement the verifyInput method:
    /*Accept only numeric characters as valid. */
public void verifyInput(ParameterValidationEvent event)
{
   if(event.text.length() > 0)
      event.allowInput = (event.text.matches("[0-9]"));
}
  3. Next, you will override the validateParameter method to display the appropriate methods depending on the values entered, as described above.
    The following pseudo code demonstrates this:
    if input = 0
   return an informational message
else if input = 1
   return a warning message
else
   return an error message
    Use the following example sample code to override this method:
    /* Returns an informational message if 0 is entered,
 * Returns a warning message if 1 is entered,
 * Returns an error message if a numeric value greater than 1 is entered
 */
public ValidationResult validateParameter(ParameterValidationevent event)
{
   ValidationResult result = new ValidationResult();
   if(event.text.contains("0"))
   {
      //Display informational message.
      result.severity = ValidationResult.INFO;
      result.message = "You entered a 0!";
   }
   else if(event.text.contains("1"))
   {
      //Display a warning message
      result.severity = ValidationResult.WARNING;
      result.message = "Values greater than 1 will result in an error!";
   }
   else
   {
      //Display an error message.
      result.severity = ValidationResult.ERROR;
      result.message = "Value is too great, enter a lower value.";
   }

   return result;
}
  4. Save the source and debug any errors.